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This study was carried out to evaluate the genetic variability among yield and yield related traits in some local rice (Oryza sativa L.) cultivars in Nigeria. The study was conducted at the Botanical Garden, Department of Botany, Ahmadu Bello University, Zaria. The seed of the rice genotypes were obtained from local farmers across the nineteen northern states of Nigeria. The experiment was laid out in Randomized Complete Block Design (RCBD) with three replications. Agronomic traits data were taken according to International Rice Research Institute Standard evaluation system. Analysis of Variance showed highly significant variation (p≤0.001) among the local rice accessions for all the agro-morphological and yield-related traits under study. A dendrogram by Unweighted Pair Group Method with Arithmetic Mean (UPGMA) grouped the rice cultivars into four cluster groups at 45.0% similarity coefficient. Principal Components (PC) analysis indicated that the first three components accounted for 80.07% of total variation. The PC1 showed 31.61%, while PC2 and PC3 exhibited 25.78 and 22.68% variability respectively among the accessions for the traits under study. The rice landraces from savanna regions of Nigeria possess enough genetic variability, this could be utilized for selection of parental genotypes for improvement by rice breeding programmes.

Drought stress negatively impacts the health of long-lived trees. Understanding the genetic mechanisms that underpin response to drought stress is requisite for selecting or enhancing climate change resilience. We aimed to determine how hybrid poplars respond to prolonged and uniform exposure to drought; how responses to moderate and more severe growth-limiting drought stresses differed; and how drought responses change throughout the day. We established hybrid poplar trees (Populus × 'Okanese') from unrooted stem cutting with abundant soil moisture for 6 weeks. We then withheld water to establish well-watered, moderate and severe growth-limiting drought conditions. These conditions were maintained for 3 weeks during which growth was monitored. We then measured photosynthetic rates and transcriptomes of leaves that had developed during the drought treatments at two times of day. The moderate and severe drought treatments elicited distinct changes in growth and development, photosynthetic rates and global transcriptome profiles. Notably, the time of day of sampling produced the strongest effect in the transcriptome data. The moderate drought treatment elicited global transcriptome changes that were intermediate to the severe and well-watered treatments in the early evening but did not elicit a strong drought response in the morning. Stable drought conditions that are sufficient to limit plant growth elicit distinct transcriptional profiles depending on the degree of water limitation and on the time of day at which they are measured. There appears to be a limited number of genes and functional gene categories that are responsive to all of the tested drought conditions in this study emphasizing the complex nature of drought regulation in long-lived trees. [ABSTRACT FROM AUTHOR]